Bio122 Lecture 12 (11/12/15)
Energy Flow & Food Webs (Ch.21), Nutrient Cycles (Ch.22)
1
I. Food Webs & Energy Flow (Ch 21)
A. Trophic levels
B. Detritus
C. Trophic pyramids
D. Energy flow differs aquatic vs. terrestrial
E. Trophic efficiency
F. Trophic cascades
G. Food webs
II. Nutrient Cycles (Ch 22 – to p. 505)
A. Nutrient requirements
B. Nutrient sources
C. Nutrient cycles
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I. Food Webs & Energy Flow (Ch 21)
1. Define trophic level
2. Draw a food chain that includes detritivores.
3. When a food chain is drawn based on boxes sized according to the numbers or total
biomass of organisms within each trophic level, why does it make a pyramid shape?
4. What ecosystem can have an inverted pyramid and why?
5. List 3 different hypotheses that have been posed to explain why terrestrial herbivores
consume a much lower proportion of autotroph biomass than aquatic ones.
6. Define trophic efficiency and list the 3 other types of ‘efficiency’ that this includes.
7. Why does assimilation efficiency tend to be lower for herbivores & detritivores than for
higher trophic levels?
8. Describe the difference between top-down and bottom-up trophic cascades. Provide an
example of each.
9. List 4 different factors that make food webs so complex.
II. Nutrient Cycles (Ch 22 – to p 505)
1. Define nutrient.
2. List 4 critical nutrients.
3. What is the ultimate source of all nutrients? How do these nutrients get released into
the environment?
4. List & briefly describe 2 properties of soil that influence the availability of nutrients for
plants and microorganisms.
5. Define leaching and note what causes it to increase.
6. Define nitrogen fixation and list 2 different ways that it can be fixed.
7. Define decomposition and briefly describe 6 factors that can influence the rate of it.
8. Define mineralization.